The invention relates to a vehicle occupant protection system comprising an inflatable gas bag, in particular a side gas bag curtain.
In curtain-like side gas bags which cover almost the complete side window of a vehicle there is often used an anchoring by means of tensioning bands to fix the gas bag, so that vehicle occupants can not be hurled out of the vehicle when the side panes break in an accident. Such an anchoring fixes the gas bag even when the gas has already escaped therefrom for the most part.
It is the object of the invention to make available a vehicle occupant protection system, including a gas bag, which allows a very fast escape or rescue of the occupant.
The invention provides a vehicle occupant protection system comprising an inflatable gas bag, a tensioning band which is tensioned in the case of inflation of the gas bag so that the tensioning band has a tensionxe2x80x94also named anchoring force in the followingxe2x80x94and a device which at the end of a predetermined period of time after inflation of the gas bag reduces the tension of the tensioning band.
When the anchoring force is reduced by the separate device arranged outside the gas bag, the gas bag can be pushed aside in order to allow the vehicle occupant to immediately get out of the vehicle, or to simplify for the rescuers the saving or first medical care of a vehicle occupant. Reduction of the anchoring force preferably takes place only after such a period of time after which the gas bag does not have to furnish a restraining effect any more.
This period of time preferably lies between 7 and 30 seconds. After this time direct follow-on accidents are not to be expected any more, the gas bag already has almost completely lost its restraining effect due to the outflow of the gas, rescuers have not yet reached the vehicle and a vehicle occupant normally tries after this time to leave the vehicle if capable to do that.
Preferably, the tensioning band is directly connected with the device. In this way the anchoring force acting on the tensioning band can be reduced in a simple manner.
The device may comprise a coupling which detaches the tensioning band from the device at the end of the predetermined period of time (which time can also be determined by a predefined tensioning path). This has the advantage that saving and self-rescue are simplified, as the gas bag can be folded aside when the tensioning band is released at one side of the gas bag.
In a preferred embodiment of the invention the device comprises a medium having a high viscosity. It is also favorable when the device comprises a medium having a variable viscosity; the medium may be an electrorheological or magnetorheological fluid.
The device preferably comprises a component which is arranged in the medium and is moved therein after the tensioning cable or band having been tensioned. It is favorable when the component is connected with the tensioning band and so the anchoring force acting on the tensioning band is transferred to the component, which force causes the component to be moved through the medium. In this manner there can be realized a simple xe2x80x9ctime switchxe2x80x9d arrangement in which the period of time can be predetermined for instance by the viscosity of the fluid, the working surface which presents the component to the fluid on moving, or the travel path through the fluid which is to be covered by the component.
In case the medium is an electrorheological or magnetorheological fluid, the viscosity of the fluid can also be influenced from outside, e.g. by a time switch or a sensor.
In a preferred embodiment of the invention the medium having high viscosity is contained in a sack. The sack preferably forms part of the device. After tightening of the tensioning band the sack may be opened to allow the medium to flow out. Through the change in the shape which can be achieved thereby, the coupling mentioned above can be actuated, for instance. Due to the high viscosity the outflow of the medium needs a specific period of time, which can be set via the viscosity of the medium.
In order to achieve an anchoring force which is sufficiently high, the tensioning band can be connected at one end with a tightening device. The tensioning band can at least in part also be tensioned by the inflation of the gas bag.
In a further advantageous embodiment of the invention the device comprises a locking mechanism which is locked by the tensioning of the tensioning band and is unlocked by a lessening of the internal pressure of the gas bag. Since the restraining effect of a gas bag drastically lessens upon lessening of its internal pressure, there is no danger at this point in time that the restraining effect of the gas bag would still be necessary. The device may work without further sensors or signal transmitters, which keeps costs low.